The influence of climate on suicidal behaviour in Italy.

A growing number of studies report an asymmetry in the seasonal distribution of suicides, with a peak in the late spring months for both sexes.

The aim of this study is to verify if the climate, apart from its seasonal change, exerts a direct influence on suicidal behaviour.

To this end, deaths by suicide in 17 Italian towns which all have a meteorologic station have been analyzed, taking into account some climatic indicators.

Results of analyses show an unequal distribution of suicides with respect to latitude, with a peak in the North.

The distribution of deaths by suicide shows a negative relationship with mean yearly temperature values, max and min, and with sun exposure indicators, and a positive, but less significant relationship with rainfall values.

As far as climatic variables considered as a whole are concerned, stepwise regression identifies three relevant factors with significant relationships to suicide rates : humidity grade, rainfall mean, and sunlight exposure.

These three climatic indicators explain up to 63% (Adj R2) of the variance in the distribution of suicide rates for both genders, with sunlight exposure offering the most significant contribution, when regressed on suicide rates via a multiple regression model.

Higher suicide rates, therefore, correspond to dry places which are less exposed to the sun. (...)